by Bryan Alexander, USA TODAY

by Bryan Alexander, USA TODAY

CANNES, France -When Oscar Isaac first approached T-Bone Burnett to prepare for his role as a folk singer in Inside Llewyn Davis, the film's executive music producer gave him some good advice.

"He told me, 'Sing like you're singing to yourself,' " Isaac recalled during a Cannes Film Festival press event on Sunday as the much-anticipated Coen brothers film made its world premiere. "That struck me for a long time."

Isaac's complicated Llewyn Davis character does open the movie singing, seemingly very much to himself. But from the sounds of the film's Cannes reception, this performance will be seen and heard by many more people.

Joel and Ethan Coen's first film since 2010's True Grit was immediately embraced by swooning critics at the festival even before Sunday's gala premiere. The Hollywood Reporter called it "outstanding" and "a singular work by the protean filmmaking team." Meanwhile, Variety called the fictional depiction of the New York 1960s folk scene a "revelatory showcase" for Isaac, who was greeted with hearty "bravos" when introduced at the press event.

As one besotted journalist asked Isaac: "Where have you come from, and where the hell are you going?"

Isaac, 33, best known for his role as Prince John in 2010's Robin Hood, didn't have a strong answer for that question. But his impressive onscreen trifecta - acting, singing, guitar playing - is speaking for itself.

"This movie is really about one character. And that one character is in almost every scene in the movie. And that character also has to be an incredible musician who sings and plays guitar," said Ethan Coen, who shared rwiting and directing duties with his brother. "I don't know how else to describe it, but we were screwed until we met Oscar."

The music veteran Burnett was beyond impressed with the talent.

"Just the odds of finding Oscar were one in 17 million," he said. "I haven't done the exact calculation."

Playing a conflicted, up-and-never-coming singer, Isaac is not alone. He's supported by a cast that includes Justin Timberlake, as Jim Berkey, a wholesome folk singer working the emerging scene alongside his wife, Jean (Carey Mulligan).

Both actors show new skills and new sides of their well-known personalities. Timberlake proudly shows off a beard and a hankering for '60s sweaters:

"I enjoy looking ridiculous," Timberlake said, "So that was not hard for me."

Mulligan, making her second appearance at Cannes following upper-class Daisy Buchanan inThe Great Gatsby, got the chance to show off an impressive singing voice and the ability to swear with great ease.

"It's like wouldn't it be interesting to do something out of left field that you haven't seen (an actor) do, but you know they can do," said co-director Joel Coen.

"And it's fun to see Carey swearing like a stevedore," added Ethan Coen.

Llewyn Davis' combative, self-destructive attitude is one reason for his seeming never-rise to success. But in fickle show business luck plays a big part, says Burnett.

"You only need a minute. There might be a reviewer from the New York Times in the audience one night, and one guy might be beat down and another guy is fresh and owns that particular moment," said Burnett. "I've seen that happen over and over again."

The cast developed their music chops with intense recording sessions before filming began, which could be released in the future along with a cast album. There is even talk of further music productions with the cast that could bring added publicity once Inside Llewyn Davis is released at the award-friendly end of the year (it begins a roll-out across the country Dec. 6).

"It's a small film so we're going to do everything we can to keep it alive," said Burnett.